An individual or family, including an elderly household, qualifies as a family of limited income if the income of the individual or family does not exceed the limits that the Secretary sets. The factors that the Secretary shall consider in setting limits under subsection (a) of this section shall include: the family income deemed available for housing; the size of the family; the ability of the family to compete successfully in the private housing market; the cost and condition of available housing; and relevant standards and definitions under federal and State housing programs.